Character generator for cathode ray tube display device

ABSTRACT

A character generator for a cathode ray tube display device generates X and Y deflection potentials and intensity control signals for the cathode ray tube by utilizing a separate storage matrix for each character with the storage elements in each such matrix being disposed where, and only where, a change is required in the direction of the X deflection, a change in the direction of the Y deflection, or a change in the intensity control signal, thereby to reduce the number of storage elements required in the storage matrices for the characters. Control signals from a selected storage matrix operate bistable storage devices which in turn operate gates to supply timing pulses to an up-down X counter and an up-down Y counter which count in either direction and convert digital quantities to analogue quantities thereby to control the vertical and horizontal deflection of the electron beam of the cathode ray tube to generate a character.

United States Patent Ambrico [541 CHARACTER GENERATOR FOR CATHODE RAYTUBE DISPLAY DEVICE I [72] Inventor: Louis E. Ambrico, Hyde Park, N.Y.

[73] Assignee: International Business Machines Corporation, Armonlc, NY.

[22] Filed: June 15, 1970 [2]] Appl. No.: 45,964

[52] us. Cl. .Q ..340/324 A, 315/18 [51] int. Cl. ..G061 3/14 [58] FieldoISearch ..340/324A [56] References Cited UNITED STATES PATENTS3,329,947 7/1967 Larrowe et a1 ..340/324 A 3,471,847 10/ 1969 McCulloughet a1.... ..340/324 A 2,766,444 10/1956 Sheftelman 340/324 A X 3,109,16610/1963 Kronenberg et a1. ..340/324 A 3,334,304 8/1967 Fournier et a1..340/324 A X 0 ON oscousa [451 Apr. 18, 1972 3,540,031 11/1970 Love..340/324A 3,422,304 1/1969 Thorpe ..'..315/l8 Primary Examiner-David L.Trafton Attorney-Ralph L. Thomas and Thomas & Thomas [57] ABSTRACT Asignals from a selected storage matrix operate bistable storage deviceswhich in turn operate gates to supply timing pulses to an up-down Xcounter and an up-down Y counter which count in either direction andconvert digital quantities to analogue quantities thereby to control thevertical and horizontal deflection of the electron beam of the cathoderay tube to generate a character.

5 Claims, 7 Drawing Figures INTENSITY CROSS-REFERENCES TO RELATEDAPPLICATIONS BACKGROUND OF THE INVENTION 1. This invention relates todisplay devices and more par ticularly to display devices which utilizecathode ray tubes to exhibit letters, numerals, characters and the likeon the face thereof.

2. In earlier types of cathode ray tube display devices it is customaryto use a main deflection system to position the electron beam at aselected site on the face of the cathode ray tube, and once the beam ispositioned at the selected site, it is manipulated by a charactergenerator to depict a selected character on the face of the cathode raytube. One such arrangement is shown in US. Pat. No. 3,337,860. Theelectron beam of the cathode ray tube is unblanked when illuminating theface of the cathode ray tube to depict the selected character, and allother movements of the electron beam are blanked. In one known type ofearlier cathode ray tube display device a character plane is providedfor each character to be displayed. Each character plane providesappropriate control signals for (l) incrementing or decrementing an Xcounter which controls the horizontal positioning of the electron beam,(2) incrementing or decrementing a Y counter which controls the verticalpositioning of the electron beam, and (3) manipulating an intensitycontrol for blanking or unblanking the electron beam thereby toilluminate the face of the cathode ray tube only when a selectedcharacter is being outlined. The X and Y counters can be incremented ordecremented to control the electron beam of the cathode ray tube asillustrated, for example in US. Pat. No. 3,422,304. Each character planeof such earlier display device constitutes a storage matrix havingvertical lines which receive timed pulses in sequence and horizontallines which in turn provide output control signals that increment ordecrement X and Y counters and manipulate the intensity control to blankorunblank the electron beam. Control signals from the selected characterplane are provided continuously throughout the generation of theselected character. Each character plane accordingly has numerousstorage elements, and this results in a character generator which isrelatively expensive to manufacture and maintain.

SUMMARY OF THE INVENTION It is a feature of this invention to provide animproved character generator for a cathode ray tube.

It is a feature of this invention to provide an improved charactergenerator for a cathode ray tube, which is less expensive to manufactureand to maintain.

it is a feature of this invention to provide. a character generatorwhich utilizes a separate storage matrix for each character, and thenumber of storage elements used in such storage matrices is reduced by acontrol arrangement which requires control signals from a selectedcharacter matrix if, and only if, there is a change to be made in the Xdeflection signal, the Y deflection signal, or the intensity contfolsignal.

In one arrangement according to this invention an improved charactergenerator for a cathode ray display device includes a plurality ofmatrix storage devices or character planes, one plane for eachcharacter, a control circuit, an up-down X counter, and an up-down Ycounter. Each character plane includes a plurality of vertical lineswhich are sequentially energized with timing pulses and a plurality ofhorizontal lines which provide control pulses to the control circuit.Storage elements disposed at selected coordinate intersections betweenthe vertical and horizontal lines are preferably read non-destructively.A first horizontal line provides control signals for incrementing the Xcounter, and a second horizon- 1 tal line'provides control signals-fordecrementing the X counter. A third horizontal line provides controlsignals for in- I crementing the Y counter, and a fourth horizontal lineprovides control signals for decrementing the Y counter. A fifthhorizontal line provides control signals which blank or unblank theelectron beam of the cathode ray tube at selected intervals during thegeneration of a character. First, second, third, fourth, and fifth Orcircuits are provided. All of the first horizontal lines of eachcharacter plane are connected to the first Or circuit, and all of thesecond horizontal lines of each character plane are connected to thesecond Or circuit. The third horizontal lines of each character planeare connected to the third Or circuit, and the fourth horizontal linesof each character plane are connected to the fourth Or circuit. The.fifth horizontal lines of each character plane are connected to thefifth 0r circuit. The control circuit includes four bistable storagedevices and four gates. The bistable storage devices preferably are flipflops, and they are connected to corresponding ones of the four gates.The first four Or circuits are connected to the complement input of thefour control flip. flops. The timing pulses applied to the verticallines of the character planes are supplied through a delay circuit tothe four gates. Those gates which are conditioned by their associatedflip flops pass the delayed timing pulses. The first gate is connectedto increment the X counter, and the second gate is connected todecrement the X counter. The third gate is connected to increment the Ycounter, and the fourth gate is connected to decrement the Y counter.The X and Y counters are connected to deflection means which positionthe beam of the cathode ray tube. The fifth Or circuit is connected to afifth flip flop which in turn is connected to an intensity controlcircuit which blanks or unblanks the beam of the cathode ray tube. Theelectron beam is unblanked to intensity or outline a character on theface of the cathode ray tube. The first through fourth flip flopscontrol the corresponding ones of the four gates thereby to increment ordecrement either or both of the X and Y counters. The electron beammoves when a character is generated. This movement may involve a changein the X direction, a change in the Y direction, or both a change in theX direction and the Y direction. Furthermore, these changes may involvemovement in the X direction which is right or left and movement in the Ydirection which is up or down. The character planes provide controlsignals through the associated Or circuits to the associated flip flopfor the purpose of controlling the X and Y counters thereby to move theelectron beam in a given manner to generate a particular character. Thestorage elements in each character plane are disposed in a fashion whichprovides control pulses on the first through the fifth horizontal linesof each character plane at the appropriate time as determined by thetiming pulses on the vertical lines thereby (1 to provide controlsignals on the first through fifth horizontal lines of the selectedcharacter plane whenever there is a change to be made in the X or Ydirection of the electron beam and (2) to unblank the electron beam atselected times to cause the character to be intensified on the face ofthe cathode ray tube. The use of storage elements in the charactermatrix to generate control signals (1 when, and

only when, there is a change in the X or.Y direction of the.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a display deviceincluding a cathode ray tube and a character generator connectedthereto, and this arrangement typifies earlier such display devices.

FIG. 2 illustrates in detail the character planes shown in block form inFIG. 1.

FIG. 2A shows a waveform which is helpful in explaining the operationofthe arrangement in FIG. 1.

FIG. 3 illustrates how the letter T is generated in a selected area ontheface of a cathode ray tube.

FIG. '4 illustrates a display device which utilizes a cathode ray tubeand an improved character generator according to this invention.

FIG. 5 illustrates in detail a character plane shown in block form inFIG. 4. 7

. FIG. 6 illustrates curves A through E which are helpful in explainingthe operation of the circuit arrangement in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT A display device according tothis invention includes a cathode ray tube and an associated charactergenerator for supplyingsignals to the cathode ray tube which control theelectron beam to trace letters, numbers, symbols-and the like on theface of the cathode ray tube. A main deflection device positions thebeam in a selected location on the face of the cathode ray tube, and thecharacter generator then supplies control signals to a characterdeflection yoke which manipulates the electron beam to generate theselected character at this location. A main deflection yoke and acharacter deflection yoke are illustrated, for example, in US. Pat. No.3,337,860.

Reference is made to FIG. 1 which illustrates a character generator 10and a cathode ray tube 12. The arrangement in FIG. 1 represents priorart, and this device is shown and described in copending applicationSer. No. 721,477 filed Apr. 15, 1968 for Symbol Generating Apparatus byWilliam R. Lamoureux. Briefly summarized, a character selection decoderselects one of the planes 16 thorough 18. Each plane is a read onlystore in which is stored information for generating a selectedcharacter. In other words there is one plane for each character to bedisplayed on the cathode ray 12. A timing pulse generator suppliestiming pulses TP1 through 'IP40 the planes 16 through 18. Signals readfrom the selected plane pass through Or circuits 40 through 44 viarespective lines 50 through 54 to operate an associated X counter 60 a Ycounter 61 and a flip flop 62. More specifically, pulses from theselected plane pass through the Or circuits 40 through 44 on respectivelines 50 through 54, and pulses on the line 50 increment the X counter60. Pulses on the line 51 decrement the X counter 60. Pulses on the line52 increment the Y counter 61, and pulses on the line 53 decrement the Ycounter 61. Pulses on the line 54 complement the flip flop 62 which inturn operates an intensity control 63 which controls the signals on thegrid 64 thereby to blank or unblank the beam of the cathode ray to 12.The X counter 60 is an up-down counter arrangement which providescontrol currents through associated character yoke drivers 71 and 72 tocontrol the current through the character yoke windings 81 and 82,thereby to control the horizontal deflection of the beam of the cathoderay tube 12. Likewise, the Y counter 61 is an up-down counter whichprovides control currents through the character yoke drivers 73 and 74to the yoke destructively by the timing pulses on theassociated-vertical lines.

The letter T is generated onthe face of the cathode ray tu '12 at alocation determined by the main deflection yoke which is not shown inthe interest of simplicity. Any spot on the face of the cathode ray tube12 may be selected by the main deflection yoke, and the characterdeflection yoke then generates the character T at the selected site. Theselected site with the character T is illustrated in the blown-up viewof FIG. 3. The main deflection yoke initially positions the electronbeam of the cathode ray tube 12 at the point 150 in FIG. 3 and thecharacter yoke controls the horizontal and vertical deflection from thepoint 150 thereby to generate the letter T. The generation of thischaracter is described next.

Referring again to FIG. 2, the tinting pulses TPl through TF4 cause therespective storage elements 101 through 104 to provide a succession ofpulses on the line 90 which pass through the 0r circuit 40 in FIG. 1 andincrement the X counter 60 four times. It thereby supplies current tothe windings 81 and 82 of the character deflection yoke which causes thebeam in FIG.-3 to move from .the reference point 150 to the right pastthe point 151. The pulse TF5 reads the memory element 105 in FIG. 2which in turn supplies a pulse on the line 91 through the Or circuit 41in FIG. 1 which decrement the X counter 60. It changes the current inthe windings 81 and 82 to move the beam to the left back to the point151. The timing pulses TF7 through TP17 in FIG. 2 read the respectivestorage elements 107 through 117 which in turn supply a sequence ofpulses on the line 92 through the Dr circuit 42 in FIG. 1 whichincrement the Y counter 61. It thereby supplies current to the windings83 and 84 of the character deflection yoke thereby to move the beam fromthe point 151 upwardly past the point 152. A storage element 108a inFIG. 2 is read simultaneously with the storage element 108 by the timingpulse TF8, and the storage element 108a supplies a signal on the line 94which operates the flip flop 62 in FIG. 1

to turn on the intensity control 63 which thereby intensifies or aresupplied through the Or circuit 40 in FIG. 1 to increment the X counter60. This changes the current in the character yoke windings 81 and 82and causes the beam to move from the point 152 in FIG. 3 to the point153. The storage element 1180 in FIG. 2 is read by the timing pulseTP18, and a resultwindings 83 and 84 thereby to control the verticaldeflection of the electron beam in the cathode ray tube. The X counter60 and the Y counter 61 may be any one of many well known in patent3,422,304.

There are as many planes in FIG. 1 as there are characters, and only onecharacter is stored in a given plane. Let it be assumed for purposes ofillustration that the plane 17 in FIG. 1 stores information forgenerating the letter T. The details of plane 17 are illustrated in FIG.2. The plane 17 is a read only store matrix having horizontal lines 90through 94 and vertical lines which receive timing pulses TF1 throughTP40. The vertical lines are designated by their timing pulse number.The horizontal lines 90 through 94 supply pulse signals to therespective Or circuits 40 through 44 in- FIG. 1. Storage elements areprovided at selected coordinate intersections of the storage array inFIG. 2, and the storage elements are read non ing pulse on the line 93is supplied through the Or circuit 43 in FIG. 1 to decrement the Ycounter 61. In this connection it is pointed out that as the beamapproaches the point 152 in FIG. 3 it overshot this point, and bydecrementing the Y counter 61, the beam is brought back to the linewhich lies between the points 152 and 153. This overshoot and return isillustrated by the dotted line 154 which is exaggerated for illustrativepurposes. The storage element a in FIG. 2 is read by the timing pulseTP20, and the resulting signal on the line 94 passes through the Orcircuit'44 in FIG. 1 to complement the flip flop 62 and deactivate theintensity control 63 which in turn blanks the electron beam.Consequently, the beam is blanked as it travels from the point 152 tothe point 153 in FIG. 3. In fact, the beam travels to the right past thepoint 153 g in FIG. 3 in response to the timing pulse TP22, and timingpulses TP23 through TP25 read the respective storage elements 123through 125 thereby to generate pulses on the line 91 which decrementthe X counter 60 in FIG. 1 and moves the beam to the left back to thepoint 153 in FIG. 3. The timing pulse TP25 reads the storage element125a in FIG. 2, and the resultant pulse on the line 94 passes throughthe Or circuit44 in FIG. 1 to complement the flip flop 62 which in turnoperates the intensity control 63 to unblank or intensify the electronbeam. The timing pulses TP25 through TP36 read respective storageelements 125 through 136 in FIG. 2, and the resultant series of pulseson the line 91 is supplied through the Or circuit 41 to decrement the Xcounter 60 in FIG. 1 and thereby change the current in the characteryoke windings 81 and 82 to move the electron beam from the point 153 inFIG. 3' to the left to the point 155. When the electron beam reaches thepoint 155 in FIG. 3, the timing pulse TP36 reads the storage element136a in FIG. 2, and the resulting pulse on the line 94 passes throughthe Or circuit 44 in FIG. 1 to complement the flip flop 62 anddeactivate the intensity control 63 thereby to blank the electron beam.The waveform in FIG. 2A illustrates when the electron beam is blankedand unblanked. The electron beam is unblanked during the period of thepositive pulses 141 and 142. As soon as the electron beam is blanked,the X counter 60 and the Y counter 61 are reset to return the beam tothe point 150 in FIG. 3. The main deflection yoke, not shown, may beoperated to move the electron beam to another site where anotherselected character may be generated.

FIG. 4 illustrates an improved character generator arrangement accordingto this invention. The reference numbers used to designate the elementsin FIG. 4 are identical to those used to designate corresponding partsin FIG. 1 except the value 200 is added to the reference number in FIG.4. For example, the character selection decoder 15 in FIG. 1 is numbered215 in FIG. 4. The system of FIG. 4 is similar to that of FIG. 1 withthe exception that an r circuit 231, a delay circuit 232 and a controlcircuit 233 are added. The control circuit 233 includes flip flops 235through 238 which are connected to respective gates 245 through 248.Signals from the Or circuits 240 through 243 control the operation ofthe flip flops 235 which in turn control the operation of respectivegates 245 through 248 to pass or inhibit pulses TPl through TP40 whichpass through the Or circuit 231 and the delay circuit 232. It is pointedout that all of the timing pulses are delayed by the delay circuit 232before being applied to the gates 245 through 248, and the amount of thedelay is sufficient to permit signals read from the selected one of theplanes 216 through 218 to pass through the Or circuits 240 through 243and operate the associated flip flops 235 through 238 thereby to controlthe associated gates 245 through 248 before the delayed signals areapplied to these gates. For example, if the plane 216 in FIG. 4 isselected and the timing pulse TPl reads a storage element which suppliesa signal to the Or circuit 240, then the amount of the time delayin thedelay circuit 232 is sufficient to permit the flip flop 235 to beoperated and condition or decondition, as the case may be, the gate 245before the delayed TF1 pulse emerges from the delay circuit 232. Thegates 245 through 248 are controlled to pass the delayed timing pulsesto the associated X counter 260 and the counter 261 which operate in themanner explained with reference to the system in FIG. 1.

It should be explained by way of introduction that characters aregenerated on the face of the cathode ray tube by visible segments orvectors disposed end to end. Each segment or vector has length anddirection. The segments or vectors vary in lengths. Each segment orvector is straight, and its direction does not change. A curved sectionof a character is generated by numerous minute, straight segments orvectors disposed end to end with each having a different direction.

It is a feature of this invention to reduce the number of storageelements in the character planes 216 through 218 in FIG. 4. This is doneby utilizing the storage elements in the planes to define change overpoints between the segments or vectors which compose a character. Inessence, therefore, the changeover points indicate a change in directionof the beam sweep. The storage elements serve to make changes in the Xand Y counters and hence alter the X and Y directions of the sweep ofthe electron beam in the cathode ray tube 212. The technique forgenerating characters on the face of the cathode ray tube 212 by thecontrol circuit 210 in FIG. 4 involves the at selected coordinateintersections to provide control signals which manipulate the controlflip flops 235 through 238 thereby to operate the associated X counter260 and the Y counter 261 to deflect the electron beam in the respectiveX and Y directions. The flip flop 235 is complemented to the one statewhenever deflection of the electron beam horizontally to the right isdesired. In this case the gate 245 is conditioned to pass the tintingpulses from the delay circuit 232, and

these pulses increment the X counter 260 to deflect the electron beamhorizontally to the right. The flip flop 236 is complemented to the onestate whenever it is desired to deflect the electron beam to the lefthorizontally. In this case the one output side of the flip flop 236resets the flip flop 235, and the one output from the flip flop 236conditions the gate 246 to pass timing pulses which decrement the Xcounter 260 and thereby sweep the electron beam horizontally to theleft. When both of the flip flops 235 and 236 are reset to the zerostate, the X counter 260 is neither incremented nor decremented, and theelectron beam does not move horizontally to the right or to the left. Ina similar fashion the control flip flops 237 and 238 control respectivegates 247 and 248 to operate the Y counter 261. The Y counter isincremented under control of the flip flop 237 to move the electron beamupwardly, and the Y counter 261 is decremented under control of the flipflop 238 to move the electron beam downwardly. When the flip flops 237and 238 are reset, the Y counter 261 is neither incremented nordecremented. In this case the electron beam does not move up or down.The flip flop 262 in FIG. 4 operates the intensity control 263 to blankor unblank the electron beam. The intensity control 263 is used tointensify or unblank the electron beam whenever the selected characteris being generated on the face of the cathode ray tube 212. Otherwise,the electron beam is blanked.

Each of the planes 216 through 218 in FIG. 4 store different characters,and only one character is stored in a given one of these planes. Let itbe assumed for purposes of illustration that the plane 217 in FIG. 4 isused to store signals for generating the letter T. The details of theplane 217 in FIG. 4 are illustrated in FIG. 5. Timing pulses TF1 throughTP40 are supplied to the vertical lines of the storage matrix in FIG. 5,and each one of the horizontal lines 290 through 294 of the storagematrix is energized with an output pulse signal each time one of thetiming pulses interrogates a storage element disposed on such horizontalline. The signals supplied on the lines 290 through 294 are controlsignals which manipulate the associated flip flops 235 through 238 and262 in FIG. 4 for the purposes outlines above. The storage elements 301through 311 in FIG. 5 are disposed at selected coordinate intersectionsas shown, and they serve the function of providing control signals togenerate the letter T. It is appropriate at this point to describe theoperation of the circuit arrangement in FIG. 4 whenever it generates theletter T on the face of the cathode ray tube 212, and for this purposelet it be assumed that the character selection decoder 215 in FIG. 4selects the plane 217.

The timing pulse generator 230 in FIG. 4 supplies timing pulses TPlthrough TP40 in succession to the memory planes 216 through 218 in FIG.4. Since the memory plane 217 is selected by the character selectiondecoder 215, these timing pulses interrogate the storage elements in theplane 217. More specifically, the timing pulses TPl through TP40 areapplied to the vertical lines of the storage array in FIG. 5. The pulseTPl interrogates the non-destructive storage element 301, and a pulsesignal is supplied on the line 290 through the Or circuit 240 in FIG. 4to the complement input of the flip flop 235. Let it be assumed thatinitially the flip flops 235 through 238 and the flip flop 262 arereset. Positive pulse signals received by the flip flops 235 through 238and 262 from the associated Or circuits 240 through 244 are effective tocomplement these flip flops. Accordingly, the positive pulse signal fromthe Or circuit 240 complements the flip flop 235 to condition the gate245. The pulse TPl in FIG. 4 is supplied also disposition of storageelements in the planes 216 through 218 through the Or circuit 231 andthe delay circuit 232 to all of the gates 245 through 248. All of thesegates are deconditioned except the gate 245, and the gate 245 thereforepasses the TPI pulse to increment to X counter 260. The output signalsfrom the control flip flops 235 through 238 and 262 are shown in FIG. 6.FIG. 6A represents the output signals from the control flip flop 235,and FIG. 68 represents the output signals from the control flip flop236. FIG. 6C depicts the out.-

put signals from the control flip flop 237 in FIG. 4, and FIG. 60 showsthe output signals from the control flip flop 238. FIG. 6E shows theintensity control signals provided by the output from the control flipflop 262 in FIG. 4. As timing pulses TF2 through TF4 occur, they areuneventful in the storage matrix in FIG. 2. However, these pulses passthrough the Or circuit 231 and the delay circuit 232, and each is passedby the gate 245 to increment the X counter 260. The X counter changesthe current in the character yoke windings 281 and 282 which therebymoves theelectron beam from the point 150 in FIG. 3 to the right pastthe point 151. When the pulse TF5 occurs, it interrogates the storageelement 302 in FIG. 5, and a positive pulse is supplied on the line 291through the Or circuit 241 to complement the flip flop 236 to the onestate which thereby conditions the .gate 246 to pass the delayed TF5pulse from the delay circuit 232. The signal from the one output side ofthe flip flop 236 resets the flip flop 235 which thereby deconditionsthe gate 245. The positive pulse from the gate 246 decrements the Xcounter 260 and changes the current in the yoke windings 281 and282 tomove the electron beam to the left back toward the point 151 in FIG. 3thereby to correct for the overshoot to the right.

The timing pulse TF6 reads the storage element 303 in FIG. 5, and theresulting positive output pulse on the line 291 passes through the Orcircuit 241 in FIG. 4 and complements the flip flop 236 to the zerostate. This deconditions the gate 246 beforethe delayed timing pulse TF6emerges from the delay circuit 232, the application of further pulses tothe X counter 260 in FIG. 4 is terminated. Hence the electron beam stopsmoving to the left, and it stops at the point 151 in FIG. 3. It ispointed out that the one output side of the flip flop 235 in FIG. 4generates a positive pulse 400 as shown in FIG. 6A. The positive pulse400 is initiated by the timing pulse TF1, and it is terminated by thetiming pulse TP5, as shown. The one output side of the flip flop 236 inFIG. 4 generates a positive pulse 401 as illustrated in FIG. 6B. Thepositive pulse 401 is initiated by the timing pulse TF5, and it istemiinated by the timing pulse TF6. All of the control flip flops 235through 238 and 262 in FIG. 4 are in the reset condition upontermination of the timing pulse TF6.

The timing pulse TF7 reads the storage element 304 in FIG. 5, and theresulting positive pulse on the line 292 passes through the Or circuit242 in FIG. 4 to complement the flip flop 237 to the one state andthereby condition the gate 247. The delayed timing pulse TF7 passesthrough the gate 247 and increments the Y counter 261, and this changesthe current in the character yoke windings 283 and 284 to move theelectron beam upwardly from the point 151 in FIG. 3. The one output ofthe flip flop 237 in FIG. 4 generates the positive pulse 402 in FIG. 6C,and the timing pulse TF7 initiates the positive pulse 402. The positivepulse 402 is terminated by the timing pulse TF18 as described more fullyhereinafter. The positive signal 402 in FIG. 6C conditions the gate247in FIG. 4 to pass the delayed timing pulses TF7 through TF17, andthese tinting pulses increment the Y counter 26] to change the currentin the character yoke deflection windings 283 and 284 to move theelectron beam upwardly from the point 151 in FIG. 3 toward the point152.

The timing pulse TF8 reads the storage element 305 in FIG. 5, and theresulting positive pulse on the line 294 passes through the Or circuit244 in FIG. 4 to complement the flip flop 262 to the one state. Thepositive signal from the one output side of the flip flop 262 operatesthe intensity control 263 and changes the signal level on the grid 264thereby to unblank the electron beam and intensify the face of thecathode ray tube 212. The electron beam illuminates the face of thecathode ray tube commenciifgatthe point 151 in FIG. 3 and continuing tothe point 152 at which time the electron beam is blanked by the timingpulse TF20 as described subsequently. The one output side of the flipflop 262 in FIG. 4 provides the positive pulse 403 in FIG. 65 to theintensity control 263. The positive pulse 403 is initiated by the timingpulse TF8, and it is terminated by the timing pulse TF20 as illustratedin 6E.

The timing pulse TF18 reads the storage element 306 in FIG. 5, and theresulting positive pulse on the line 290 passes through the Or circuit240 in FIG. 4 to complement the flip flop 235 to the one state whichthereby conditions the gate 245 to pass the delayed timing pulse TF18 toincrement the X counter 260. Incrementing the X counter 260 causes theelectron beam to move to the right in FIG. 3 from the vicinity of thepoint 152 toward the point 153. The one output side of the flip flop 235continues as a positive level until the timing pulse TF23 occurssubsequently, and this output level is depicted as the positive pulse404 in FIG. 6A. This positive output signal conditions the gate 245 topass each of the timing pulses TFI8 through TF22, and each incrementsthe X counter 260 thereby to move the electron beam toward theright'until it reaches the point 153 in FIG. 3.

The timing pulse TF18 also reads the storage element 306a in FIG. 5, andthe resultant positive pulse on the line 293 passes through the Orcircuit 243 in FIG. 4 to complement the flip flop 238 to the one statewhich thereby conditions the gate 248 to pass the delayed timing pulseTP18 to decrement the Y counter 261. Decrementing the Y counter 261causes the electron beam to move downwardly in FIG. 3 to correct for theovershoot depicted by the dotted line 154. The positive output signalfrom the one side of the flip flop 238 generates a positive pulse, andthis is shown as the pulse 405 in FIG. 6D. This positive pulseterminates with the timing pulse TPl9 as explained subsequently. Thepositive signal from the one output side of the flip flop 238 is appliedto the zero input side of the flip flop 237, and it is effective toreset the flip flop 237 and thereby terminate the positive output signalfrom the one output side of the flip flop 237 which thereby deconditionsthe gate 247. This action terminates the positive pulse 402 in FIG. 6C.

The timing pulse TF19 reads the storage-element 307 in FIG. 5, and theresultant positive pulse on the line 293 passes through the Or circuit243 in FIG. 4 to complement the flip flop 238 to the zero state, andthis terminates the positive pulse 405 in FIG. 6D. Consequently, thegate 248 in FIG. 4 is deconditioned to prevent further decrementing ofthe Y counter 261, and compensation has been completed for the verticalovershoot depicted by the dotted line 154.

The timing pulse TF20 reads the storage element 308 in FIG. 5, and theresultant positive pulse on the line 294 passes through the Or circuit244 in FIG. 4 and complements the flip flop 262 from the one state tothe zero state. This deactivates the intensity control 263 and therebyblanks the electron beam. This action causes the termination of thepositive pulse 403 in FIG. 6E. The delayed pulses TP18 through TP22 passthrough the gate 245 in FIG. 4 to increment the X counter 260 andthereby move the electron beam to the right from the vicinity of thepoint 152 in FIG. 3 to the point 153.

When the timing pulse TF23 occurs, it reads the storage element 309 inFIG. 5, and the resultant positive pulse on the line 291 passes throughthe Or circuit 241 in FIG. 4 and complemerits the flip flop 236 to theone state which thereby conditions the gate 246. The positive signalfrom the one output side of the flip flop 236 is shown as the positivepulse 406 in FIG. 6B. The positive output signal from the one outputside of the flip flop 236 is supplied to the zero input side of the flipflop 235, and it is effective to reset this flip flop to the zero state.This terminates the positive pulse from the one output side of the flipflop 235 which is shown as the pulse 404 in FIG. 6A. The timing pulsesTF23 through TP40 are passed by the gate 246 to decrement the X counter260 which in turn changes the current through the character yokewindings 281 and 282 to move the electron beam from the vicinity of the9 point 153 in FIG. 3 to the left toward the point 155 thereby togenerate the upper portion of the letter T.

The timing pulse TP25 reads the storage element 310 in FIG. 5, and theresulting positive pulse on the line 294 passes through the Or circuit244 in FIG. 4 and complements the flip flop 262 to the one state toinitiate the positive pulse 407 in FIG. 6E. The positive output pulse407 from the one side of the flip flop 262 operates the intensitycontrol 263 to supply a signal level to the grid 264 which unblanks theelectron beam. The line between the point 153 in FIG. 3 and the point155 is intensified as the electron beam sweeps to the left between thesetwo points in response to timing pulses TP23 through TP36.

The timing pulse TP36 reads the storage element 311 in FIG. 5, and theresulting positive pulse on the line 294 passes through the Or circuit244 and complements the flip flop 262 from the one state to the zerostate. This terminates the positive pulse 407 from the one side of theflip flop 262 in FIG. 4 and thereby deactivates the intensity control263 which supplies a signal level to the grid 264 that blanks theelectron beam as it reaches the point 155 in FIG. 3. Thus the letter Tis generated on the face of this cathode ray tube 212. Once the electronbeam is blanked by the timing pulse TP36, the flip flops 235 through 238in FIG. 4 may be reset to return the electron beam to the point 150 inFIG. 3. The character yoke may then position the electron beam, to a newlocation where another selected character may be generated.

The storage elements in FIG. 5 are disposed in the read only storagematrix in a fashion which provides control pulses on the horizontallines 290 through 294 at the appropriate times as determined by thetiming pulses on the vertical lines. It is pointed out in thisconnection that the positive pulse 400 in FIG. 6A is initiated bythe'storage element 301, and the positive pulse 400 is terminated by theaction of the storage element 302. During the interim the X counter isincremented by the delayed timing pulses TPI through TP4, and theelectron beam moves from the point 150 in FIG. 3 to the point 151.Actually, the beam moves past the point 151, and this overshoot iscorrected by decrementing the X counter 260. This decrementing is doneunder control of the pulse 401 in FIG. 6B which is initiated andterminated under control of respective storage elements 302 and 303.Then the positive pulse 402 in FIG. 6C is initiated by the storageelement 304, and it is terminated by the action of the storage element306A. For the duration of the positive pulse 402 the delayed timingpulses TP7 through TP17 increment the Y counter 261 in FIG. 4 to movethe electron beam from the point 151 in FIG. 3 to the point 152. Thepositive pulse 403 is generated next. It is initiated by the action ofthe storage element 305 and terminated by the action of the storageelement 308. The electron beam is unblanked and for the duration of thepulse 403. The positive pulse 404 in FIG. 6A is generated. It isinitiated by the action of the storage element 306, and it is terminatedby the action of the storage element 309. For the duration of thepositive pulse 404 the timing pulses TP18 through TP22 increment the Xcounter 260 in FIG. 4, and this moves the electron beam from the point152 in FIG. 3 to the point 153. The positive pulse 405 in FIG. 6D isgenerated to decrement the Y counter 261 in FIG. 4 and correct forvertical overshoot. The positive pulse 405 is initiated and terminatedby action of the respective storage elements 306a and 307 in FIG. 5.Next the positive pulse 406 in FIG. 6B is generated. The positive pulse406 is initiated by the action of the storage element 309, and thepositive pulse 406 continues until the end of this character period. Thetiming pulses TP23 through TP40 decrement the X counter 260 in FIG. 4thereby to move the electron beam from the point 153 in FIG. 3 towardthe point 155. The electron beam is unblanked for the duration of thepositive pulses 403 and 407 in FIG. 65. During the positive pulse 403the electron beam is intensified as it moves from the point 151 in FIG.3 to the point 152 as pointed out above, and during the positive pulse407 the electron beam is intensified as it moves from the point 153 inFIG. 3 to the point 155. The

election beam is blanked upon termination .of the positive pulse 407 inFIG. 6E which occurs at timing pulse TP36. It is seen that storageelements are used in FIG. 5(1) to provide control signals on the lines290 through 294 whenever there is a change in the X or Y direction ofthe beam during the generation of a character and (2) to unblank theelectron beam at selected times to cause the character to be intensifiedon the face of the cathode ray tube.

The use of storage elements in the matrix of FIG. 5 to generate controlsignals (I) when, and only when, there is a change in the X or Ydirection of the beam or 2) a change in intensity of the electron beamresults in the use of relatively fewer storage elements for generatingthe letter T. This readily may be seen by comparing the number ofstorage elements in the matrix array in FIG. 5 with the number ofstorage elements in the matrix array in FIG. 5 with the number ofstorage elements in the matrix array of FIG. 2. The storage matrix inFIG. 2 uses 40 storage elements; whereas, the storage array in FIG. 5uses 12 storage elements. Hence the storage array in FIG. 5 provides asubstantial decrease in the number of storage elements employed forgenerating the character T over the number of storage elements employedin the matrix array of FIG. 2 for generating the character T. It ispointed out that a separate storage array is provided for each characterin the arrangements of FIGS. 1 and 4. It is noted further that not everyone of the arrays 216 through 218 in FIG. 4 provides the same degree ofreduction in storage elements over the corresponding array in FIG. 1. Amore favorable reduction in storage elements is obtained over thecorresponding array in FIG. 1 for those arrays in FIG. 4 which generatecharacters having substantially straight lines such as X, T, I, and thelike. These characters involve a minimal number of changes in directionof the electron beam of the cathode ray tube. Character planes in FIG. 4which generate characters having a substantial number of changes in theX and Y directions of the electron beam provide a substantially lessfavorable reduction of storage elements over the corresponding plane inFIG. 1, and in some characters there may be no saving in storageelements at all over the character arrays of FIG. 1. For example,characters such as Q, 0, G and the like require constant changes in theX and Y directions of the electron beam, and such character planes inFIG. 4 require a substantial number of storage elements. However, if thenumber of character planes included in FIGS. 1 and 4 provide for thegeneration of the letters A through Z and the numbers 0 through 9, thenthe total number of storage elements employed in the planes of FIG. 4become substantially less than the total number of storage elementsemployed in the planes of FIG. 1.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

l. A display device composed of a cathode ray tube and a charactergenerator coupled thereto for generating characters on the face of thecathode ray tube, the character generator including:

a plurality of character planes, selection means coupled to theplurality of character planes for selecting any one of the characterplanes, each character plane including a matrix array of vertical linesand horizontal lines, said horizontal lines including first, second,third, fourth, and fifth horizontal lines, a plurality of storageelements, said storage elements being disposed only at such coordinateintersections of the vertical and horizontal lines where a change in thehorizontal deflection, a change in the vertical deflection, or a changein intensity are required for controlling the electron beam of thecathode ray,

pulse generator means connected to the vertical lines for applyingtinting pulses sequentially to the vertical lines of a selectedcharacter plane, each storage element responding to a timing pulse onthe associated vertical line to provide a control pulse on thecorresponding horizontal line,

first, second, third, fourth and fifth bistable storage devices, meansinterconnecting the first and second bistable storage devices to inhibitoperation of both of these bistable storage devices at the same time,means interconnecting the third and fourth bistable storage devices toinhibit operationof both of these bistable storage devices at the sametime, means coupling the first, second, third, fourth and fifthhorizontal lines of each character plane to the respective first,second, third, fourth and fifth bistable storage devices,

first, second, third, and fourth gates, means connecting the first,second, third, and fourth bistable storage devices to the respectivefirst, second, third, and fourth gates, means connected between thepulse generator means and said gates for supplying each timing pulsedelayed in time to each of said gates,

said cathode ray tube having vertical deflection means and horizontaldeflection means,

first means connected between the horizontal deflection means and thefirst and second gates for controlling the horizontal deflection of theelectron beam of said cathode ray tube,

second means connected between the vertical deflection devices areflip-flops, the first means is an up-down X counter, and the secondmeans is an up-down Y counter.

3; The apparatus of claim 2 wherein said means connected between thetiming pulse generator and said gates includes an Or circuit and a delaycircuit serially connected between the pulse generator means and saidgates.

4. A display device including:

a cathode ray tube, said cathode ray tube having vertical deflectionmeans and horizontal deflection means,

first means connected to the horizontal deflection means for controllingthe horizontal deflection of the electron beam of said cathode ray tube,second means connected to the vertical deflection means for controllingthe vertical deflection of the electron beam of the cathode ray tube,first and second gates connected to said first means, third and fourthgates connected to said second means,

first and second bistable storage devices connected to the respectivefirst and second gates, third and fourth bistable storage devicesconnected to the respective third and fourth gates, meansinterconnecting the first and second bistable storage devices to inhibitoperation of both of these bistable storage devices at the same time,means interconnecting the 7 third and fourth bistable storage devices toinhibit operation of both of these bistable storage devices at the sametime,

a plurality of character planes, selection means coupled to theplurality of character planes for selecting any one of the characterplanes, each character plane including a matrix array of vertical linesand horizontal lines, said horizontal lines including first, second,third, fourth, and fifth horizontal lines, a plurality of storageelements, said storage elements being disposed at such coordinateintersections of the vertical and horizontal lines only where a changein the horizontal deflection, a change in the vertical deflection, or achange in intensity are required for controlling the electron beam ofthe cathode ray tube,

pulse generator means connected to the vertical lines for applyingtiming pulses sequentially to the vertical lines of a selected characterplane, each storage element responding to a timing pulse on theassociated vertical line to provide a control pulse on the correspondinghorizontal line,

intensity control means connected to said cathode ray tube, a fifthbistable storage device connected to said intensity control means, meansconnecting the first, second, third, fourth, and fifth horizontal linesof each character planes to the respective fust, second, third, fourth,and fifth bistable storage devices, and

an 0r circuit and a delay circuit connected in series, said Or circuitbeing connected to said pulse generator means to supply all timingpulses to said delay circuit, and said delay circuit being connected tosaid first, second, third, and fourth gates to supply all timing pulsesdelayed in time to said gates.

5. The apparatus of claim 4 wherein the first means is an updown Xcounter, the second means is an up-down Y counter, and the bistablestorage devices are flip-flops.

1. A display device composed of a cathode ray tube and a charactergenerator coupled thereto for generating characters on the face of thecathode ray tube, the character generator including: a plurality ofcharacter planes, selection means coupled to the plurality of characterplanes for selecting any one of the character planes, each characterplane including a matrix array of vertical lines and horizontal lines,said horizontal lines including first, second, third, fourth, and fifthhorizontal lines, a plurality of storage elements, said storage elementsbeing disposed only at such coordinate intersections of the vertical andhorizontal lines where a change in the horizontal deflection, a changein the vertical deflection, or a change in intensity are required forcontrolling the electron beam of the cathode ray, pulse generator meansconnected to the vertical lines for applying timing pulses sequentiallyto the vertical lines of a selected character plane, each storageelement responding to a timing pulse on the associated vertical line toprovide a control pulse on the corresponding horizontal line, first,second, third, fourth and fifth bistable storage devices, meansinterconnecting the first and second bistable storage devices to inhibitoperation of both of these bistable storage devices at the same time,means interconnecting the third and fourth bistable storage devices toinhibit operation of both of these bistable storage devices at the sametime, means coupling the first, second, third, fourth and fifthhorizontal lines of each character plane to the respective first,second, third, fourth and fifth bistable storage devices, first, second,third, and fourth gates, means connecting the first, second, third, andfourth bistable storage devices to the respective first, second, third,and fourth gates, means connected between the pulse generator means andsaid gates for supplying each timing pulse delayed in time to each ofsaid gates, said cathode ray tube having vertical deflection means andhorizontal deflection means, first means connected between thehorizontal deflection means and the first and second gates forcontrolling the horizontal deflection of the electron beam of saidcathode ray tube, second means connected between the vertical deflectionmeans and the third and fourth gates for controlling the verticaldeflection of the electron beam of the cathode ray tube, and intensitycontrol means connected between the cathode ray tube and the fifthbistable storage device for controlling the intensity of the display onthe face of the cathode ray tube.
 2. The apparatus of claim 1 whereinthe bistable storage devices are flip-flops, the first means is anup-down X counter, and the second means is an up-down Y counter.
 3. Theapparatus of claim 2 wherein said means connected between the timingpulse generator and said gates includes an Or circuit and a delaycircuit serially connected between the pulse generator means and saidgates.
 4. A display device including: a cathode ray tube, said cathoderay tube having vertical deflection means and horizontal deflectionmeans, first means connected to the horizontal deflection means forcontrolling the horizontal deflection of the electron beam of saidcathode ray tube, second means connected to the vertical deflectionmeans for controlling the vertical deflection of the electron beam ofthe cathode ray tube, first and second gates connected to said firstmeans, third and fourth gates connected to said second means, first andsecond bistable storage devices connected to the respective first andsecond gates, third and fourth bistable storage dEvices connected to therespective third and fourth gates, means interconnecting the first andsecond bistable storage devices to inhibit operation of both of thesebistable storage devices at the same time, means interconnecting thethird and fourth bistable storage devices to inhibit operation of bothof these bistable storage devices at the same time, a plurality ofcharacter planes, selection means coupled to the plurality of characterplanes for selecting any one of the character planes, each characterplane including a matrix array of vertical lines and horizontal lines,said horizontal lines including first, second, third, fourth, and fifthhorizontal lines, a plurality of storage elements, said storage elementsbeing disposed at such coordinate intersections of the vertical andhorizontal lines only where a change in the horizontal deflection, achange in the vertical deflection, or a change in intensity are requiredfor controlling the electron beam of the cathode ray tube, pulsegenerator means connected to the vertical lines for applying timingpulses sequentially to the vertical lines of a selected character plane,each storage element responding to a timing pulse on the associatedvertical line to provide a control pulse on the corresponding horizontalline, intensity control means connected to said cathode ray tube, afifth bistable storage device connected to said intensity control means,means connecting the first, second, third, fourth, and fifth horizontallines of each character planes to the respective first, second, third,fourth, and fifth bistable storage devices, and an Or circuit and adelay circuit connected in series, said Or circuit being connected tosaid pulse generator means to supply all timing pulses to said delaycircuit, and said delay circuit being connected to said first, second,third, and fourth gates to supply all timing pulses delayed in time tosaid gates.
 5. The apparatus of claim 4 wherein the first means is anup-down X counter, the second means is an up-down Y counter, and thebistable storage devices are flip-flops.